[CMB]

Most levels/platforms are sold for barred cages. You may find a Trixie platform. Making one is probably best as it will fit better.

If you measure the tank front to back, you may be able to buy or make a house with a flat roof. The roof would then work as a platform/level.

A bendy bridge is a good toy, as it can be climbed over or under.

Some chew toys that hang from the top bars may be nice.

A corner litter tray or rectangular/square ceramic bowl may be better for the sand area. It may be used by your hamster as a pee area. This means you don’t have to change the substrate as often. You just remove the damp sand and add some fresh sand.

Possibly swap the arch to the back corner and have the big wicker tube going straight across the tank, either at the front against the glass or a little further back.

A Sputnik could be added to the roof bars, but you would also need something to allow your hamster to get up to the Sputnik.